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Abstract

We report the distribution of Sparganium subglobosum Morong (Typhaceae) for the first time in Korea. Sparganium subglobosum is readily distinguishable from other Korea Sparganium species by having a short plant height, narrow leaves (≤ 4 mm), thin inflorescence branches, and a ripe fruiting head globose and ca. 1 cm in diam. The species is under great threat of local extinction due to a recent disturbance of one of only two known distribution sites. Further conservation plans for S. subglobosum and surveys are needed. We provide a revised key to five Sparganium species of Korea, with descriptions, pictures, and figures of S. subglobosum.

Sparganium is a genus of ±14 aquatic species, distributed in temperate and cool regions of Eurasia and North America, also in Oceania (Cook and Nicholls, 1986, 1987). Sparganium species are perennial herbs, emergent from shallow water or wholly submerged and floating, and comprise the most important plants in the riverside and lakeshore wetlands plant communities (Kubitzki, 1998). Also, they provide shelters and food for wildlife, and help reduce erosion of river banks (Cook and Nicholls, 1986). Sparganium species show morphological adaptations common to many other aquatic plant groups, such as monoecy, wind-pollination, floral reduction, seeds capable of long-distance dispersal, and vegetative propagation by rhizomes and stolons (Cook, 1988; Barrett et al., 1993; Santamaria, 2002). Sparganium has traditionally been placed in the monogeneric family Sparganiaceae, but recent classification scheme placed both Typha and Sparganium in Typhaceae (The Angiosperm Phylogeny Group, 2016). Sparganium is characterized by globose head-like inflorescence, while Typha is elongate, cylindrical spike-like (Kubitzki, 1998).

While working on DNA barcoding of Korean Typhaceae, including both Sparganium and Typha, we have recognized a Sparganium species new to flora of Korea, distinct from other Korean taxa both in overall morphology and sequence characteristics (data not shown). The new Sparganium species was identified as S. subglobosum Morong. Although Sun and Simpson (2010) suggested the presence of S. subglobosum in Korea, no one has ever reported or provided evidence proving the presence of S. subglobosum so far. Here we are presenting a description and diagram of S. subglobosum, and a revised key to Sparganium species in Korea.

Based on the gross morphology, we initially assigned this unrecorded Sparganium species to S. japonicum. Upon closer examination, however, it was clear that the obovoid fruits of unrecorded species did not match S. japonicum (fusiform) (Cook and Nicholls, 1987). The narrower leaves and smaller size of the species is unique among other Korean Sparganium species, except S. hyperboreum. Thus we named S. subglobosum as Ka-neun-heuk-sam-reung (가는흑삼릉), although Chinese vernacular name is 狭叶黑三棱, also meaning narrow leaved Sparganium, to avoid confusion with the Korean name of S. hyperboreum, Jop-eun-ip-heuk-sam-reung (좁은잎흑삼릉).

Sparganium subglobosum was first described from the collections made by the U.S. Exploring Expedition to Bay of Islands, New Zealand (Morong, 1888). This species is one of only two Sparganium species appears in Southern Hemisphere in Australia and New Zealand, showing disjunct distribution from Eastern Asia (Far Eastern Russia, northern China, Korea, Japan) to New Zealand, discontinously occurring in Yunnan, Vietnam, and New Guinea (Cook and Nicholls, 1987). The other species appearing in Southern Hemisphere is S. erectum, but probably introduced recently (Cook and Nicholls, 1987).

We have collected S. subglobosum from inlet of Lake Cheonjin, Goseong-gun, Gangwon Prov., where other endangered flowering plants, such as Nymphaea pygmaea var. minima and Brasenia schreberi, are also distributed. The other collection is made from wetland of Buk River (Bukcheon) near Bukcheon Bridge in Ganseong-eup, Ganseong-gun, Gangwon-do, where S. erectum and S. japonicum is also collected. The two collection sites strongly suggest that S. subglobosum may distributed in wetlands along the eastern coast of Korea. Unfortunately, collection of S. subglobosum was only made from Lake Cheonjin during the 2010–2014 floristic survey project on the lagoon areas on the eastern coast of Korean Peninsula by National Institute of Biological Resources (NIBR), whose results presented in Kim et al. (2017) (also see Specimen examined). The inlet of Lake Cheonjin has recently been reclaimed by landowner and most of the habitat has been disappeared. Dr. Jin-Seok Kim at NIBR (pers. comm.) was able to find only a few individuals of S. subglobosum surviving this year. Although the Lake Cheonjin is very important and only habitat for several endangered plant species of Korea and the threat of disturbance has been expected, no serious measures and conservation action has been taken so far. Thus, conservation plans need to be prepared and enacted immediately, to protect the endangered species. Also, further survey of the coastal wetlands need to be done, to identify new distribution sites of S. subglobosum.

Acknowledgments

Authors thank anonymous reviewers for their helpful comments on this manuscript. We also thank Drs. Goro Kokubugata and Tanaka Nobuyuki at National Museum of Nature and Science herbarium (TNS), Prof. Noriaki Murakami and Dr. Yukira Mochida at Makino Herbarium of Tokyo Metropolitan University (MAK), and Prof. Hidetoshi Nagamasu at Kyoto University Museum (KYO) for their help with herbarium work. Mr. Wunggi Lee at Daegu University made the drawing of S. subglobosum. This work was a product of the “DNA Barcode System for Korean Indigenous Plant Species (I)” project (NIBR201513201) of the National Institute of Biological Resources (NIBR), Ministry of Environment (MoE), Republic of Korea.

The Angiosperm Phylogeny Group. 2016. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of Linnean Society 161: 105-121.